Periodic mercury relay



July 28, 1964 l. l.. MITCHELL 3,142,736

Y PERIoDIc MERCURY RELAY Filed oct. 31, 1961 ,l//ll l l :AI a 7 u L3? I4 l w7:/ 2 26 .f t f/ 24f- 2 I I @2 l)E50 llllll E Ill/Il :si: /f r: e2 9 f I 11"/ l I 25 40;" 44 INvmn-OR 52 48 Ilzvme LMITCHELL,

5 '2C BY ATTORNEY;

United States Patent O 3,142,736 PERIODIC MERCURY RELAY Irving L. Mitchell, Rockville Centre, N.Y., assignor to Ebert Electronics Corporation, Queens Village, NX., a corporation of New York Filed Oct. 31, 1961, Ser. No. 149,013 11 Claims. (Cl. 200-112) This invention relates to mercury relays of the displacer type, and more particularly to mercury relays of the periodic type wherein a pool of mercury in a container is periodically displaced by a movable armature to periodically bridge two spaced electrodes located in the container, in order to periodically energize a load.

In the design of mercury timing relays, and more particularly in periodic relays employed to periodically energize a load, it is difficult to provide a construction which maintains constant operating characteristics over a long period of time during which there occurs heavy use of the relay. One of the principal disadvantages in prior mercury relays is the fact that frictional resistance between the moving parts causes changes in the working characteristics of the mercury relays, so that, for example, in mercury relays utilized to periodically energize and de-energize loads, the periodicity changes. Moreover, in those mercury timing relays which rely upon metering devices to meter either mercury or a trapped gas in a container, changes in exterior conditions have an effect on operating characteristics. For example, a change in temperature has an effect on the viscosity of a gas in a container. Another disadvantage in prior art relays is that in cases where containers having properties of electrical conduction are used, insulation and shielding may be needed between the movable elements displacing the mercury inside the container and the container itself. The existence of eddy currents due to the use of magnetically permeable materials for the container causes the operating characteristics of such mercury relays to vary as a function of the duration of use.

These and other disadvantages are overcome by the present invention in which there is provided an envelope fabricated of material which is chemically and electrically inert for example, nylon or nylon filled with fiberglass, said material also having the properties of being selflubricative. A mercury displacing element positioned for movement inside of said container is provided with studs mounted thereon for sliding frictional engagement with the container, said studs also being made of a selflubricative material, and being chemically and electrically inert. Examples of suitable materials for the studs are nylon or Delrin. The mercury displacing element of the invention is in the form of an inverted dome with a metering orifice on its bottom, and includes an outer tubular armature portion of magnetic material on which the aforementioned studs are mounted, and an inner liner portion made of a material which is chemically `and electrically inert, such as, a ceramic. An electromagnetic coil is located to surround the envelope, and mounted inside the envelope are resilient means which tend to hold the aforesaid mercury displacing element in a position beneath the level of the pool of mercury in the envelope against the tendency of the mercury displacing member to rise in the mercury to a normal buoyant position therein. A pair of spaced electrodes extend into the envelope, at least one from above in alignment with the inverted dome and are sealed Vthereto by conventional means. The spaced electrodes are connected in series with the electromagnetic energizing coil.

When the electromagnetic coil is energized by a suitable source of alternating or direct current, the mercury displacing element is moved upwardly against the compression of the spring, thereby displacing the mercury in the inverted dome through the metering orifice, and simultaneously lowering the level of mercury in the envelope. The general level of the mercury in the envelope is lowering, when the inverted dome is raised, to a level below that of the electrodes. However, the mercury trapped in the inverted dome then bridges the electrodes, so that the normally closed circuit remains closed. In the course of time the mercury in the inverted dome is discharged through the metering orifice, in sufficient quantity to unbridge the electrodes. The breaking of the electrical contact between the spaced electrodes in the container causes the coil to be de-energized. Upon de-energization of the coil, the compression spring forces the mercury displacing member downwardly in the container thereby displacing through the orifice suicient mercury upwardly to re-establish electrical contact between the spaced electrodes. Thus there is produced a periodical making and breaking of electrical contact in the relay. By connecting a suitable load in parallel with the energizing coil, said load may be periodically energized at the frequency of operation of the relay.

A feature of the invention is the provision of a mercury displacing element the inner liner portion of which is in the form of an inverted dome having an orifice therein. The size of the orifice may be varied either during manufacture or by providing threaded portions in constant sized holes in the dome, to receive screw plugs, the screw plugs having orifices of different siz. By selecting screw plugs with the appropriate size orifices, the periodicity of the relay may be varied.

Accordingly, it is an object of this invention to provide a mercury relay of the periodic type which is rugged, reliable over a long period of usage, and consistent in its operating characteristics under variable external conditions.

It is another object of the invention to provide a mercury relay to periodically energize and de-energize a load, the consistency of time operation of said mercury relay being insured by the provision of self-lubricating surfaces of low frictional resistance between the moving parts therein.

It is a further object of the invention to provide, a mercury relay of such design that the movable parts therein are of a chemically and electrically inert material, thereby minimizing the need for additional insulating and shielding material.

It is yet another object of the invention to provide a mercury relay having a minimum of friction between the moving parts therein, thereby to eliminate a change in the relationships between the moving parts due to wear, in order to provide consistency of operation over a long period of time.

These and other objects and features of the invention will be better understood by referring to the drawings in which:

FIGURE 1 is a longitudinal view in cross section of a mercury relay according to the invention;

FIGURE 2 is a schematic diagram of a circuit incorporating the relay, and

FIGURE 3 is a modified view in cross section of a further embodiment of a mercury relay according to the invention.

Referring to FIGURE l, a mercury relay according to the invention is shown generally at 10, having an envelope 12 which may be of nylon, Delrin, or preferably of nylon filled with fiberglass. The advantage of using nylon or fiberglass filled nylon -for the material of the envelope is that this type of material, in addition to being an insulator, has self-lubricating properties which minimize fnictional wear in the relay. At one end of the container 12 are spaced electrodes 14 and 16 extending thereinto in a downward direction and suitably sealed into the container by conventional means. The leads for the electrodes 14 yand 16 are designated 1S and 2% respectively. Surrounding the container 12 is an electromagnetic energizing coil 22.

The electrode lleads 18 and 2% are connected respef tively to terminals 24 `and 26. One end of coil 22 is connected to terminal 25 and the other end to terminal 27. A lead 29 connects terminals 25 and 27. As shown in the schematic diagram of FGURE 2, a line having a suitable source of DC. or A.C. supply voltage is connected to terminals 24 and 25, and the load is connected at terminals 25 and 26, thereby placing the coil 22 in series with the line, the electrodes 14 land 16 in series with the coil, and the load across coil 22.

Inside the container 12 is `a pool of mercury 28, the top level of which is indicated at 3i). Mounted inside of vthe container at the upper end is a compression spring 32.

A mercury displacing plunger 34 in the general form of an inverted dome having an oriice 49 in the dome portion thereof is positioned in the container for longitudinal up and down movement therein, said plunger being buoyant in the pool of mercury. Plunger 34 includes an outer armature portion 36 in the general form of a tube, responsive to the electromagnetic eld of energizing coil 22. An inside liner portion 38 of said plunger is in the form of `an inverted dome and is an insulator preferably made of a ceramic material. The dome portion of plunger 3S has an orice 49. Mounted on `the tubular armature portion yof the plunger are studs indicated `at 42. The studs are preferably of a material having self-lubricating properties, such as nylon or Delrin. The studs 42 are in sliding, self-lubricative frictional engagement with the inner surface of the container 12. The strength of compression spring 32 is suicient to hold the plunger 34 beneath the surface of the mercury, that is, below its normal position of buoyant equilibrium in the mercury -pool 23. A cushioning spring 29 is provided in the container 12 to protect the relay against shock.

In the operation of the embodiment shown in FGURE l, upon energization of the coil 22 from a suitable source of alternating or direct current, the plunger 34 is attracted upwardly in the container 12 against the bias of the spring 32 tending to hold the plunger in its lower position in the pool of mercury 2e in container 12. The plunger 34, now rising in container 12, causes the level 3@ of the `rnercury to be displaced, primarily through oriiice 4@ to a lower level in the container 12. During the upward progress of the plunger 34, the level 30 ot the mercury passes beneath the lower ends of electrodes 14 and 16, thereby breaking the electrical contact therebetween. Upon the breaking of the electrical Contact between the electrodes 14 and 16, which form a series connection with the coil 22, the coil 22 is de-energized. Upon de-energization of the coil 22, the force of compression spring 32 is sufficient to push plunger 34 downwardly in the container 12 thereby raising the level ot the mercury Btl to the level shown in the iigure. At some point in the rising of level iof the displaced mercury, contact between the electrodes 14 and 16 is re-established as the level 3i) passes the ends of the electrodes 14 and 16. Upon reestablishvment of electrical contact between the electrodes, the coil 22 is again energized thereby causing a repetition of the cycle just described.

Another embodiment of the relay according to the invention is shown in FIGURE 3 wherein the spaced electrodes are located at opposite ends of a container. A C011- tainer 44 is provided with an insulated electrode 46 -at the upper end and a bare electrode 4S at the lower end thereof suitably sealed therein. Insulated electrode 46 has Ia bare end suitably bonded or fused to cup Si) comprised of insulating material. A pool of mercury 52 -in said container is normally displaced by a mercury displacing armature 34 through the bias action of a compression spring 32 so that the mercury level is normally i above the level of cup 59. The mercury displacing yarmature 34 has an oriice 4i? and is preferably of the same design as `armature 34 of FIGURE l.

An energizing coil 22 surrounds a portion of the container 44 and is located to actuate movement of mercury displacing `armature S4 when energized in the same manner `as explained in conjunction with FIGURE 1. The leads for electrodes 46 and 48 lare designated as 18 and 2i) respectively, and they are connected to the terminals 24 and 26. A lead 29 connects terminals 26 and 27, and the load and line are connected to the relay terminals of FIG- URE 3 in the same manner as described-in conjunction with the schematic diagram of FIGURE 2. Thus the relays of FGURES l `and 3 provide periodic operation of a load in the same manner.

ln the operation of the embodiment of FIGURE 3, when coil 22 is energized, the mercury displacing armature 34 is pulled upward in container 44 thereby displacing the mercury of pool 52 primarily through orifice 4i). As the armature 34 ascends, the level of mercury drops below Vthat of cup Sti, thereby breaking electrical Contact between electrodes 46 and 43 and cutting of line power to the coil 22. When coil 22 is thus cle-energized, compression spring 32 urges armature 34 downwardly into the mercury pool 52 thereby displacing the mercury upwardly to exceed the level of the cup 5d, thereby re-establishing contact between the spaced electrodes 46 and 48.

The speed at which the plunger 34 rises up and down in the pool or" mercury 28 is adjustable by varying the size of the orice 49. Although the speed of the action of plunger 34 may also be varied by varying the compressive force of spring 32, it is much more convenient to vary the speed of the action of plunger 34 by varying the size of orifice di), since it is much cheaper and easier to merely mass produce parts such as the inverted dome plunger 34 having various size orces therein. Alternatively all of the inverted dome plungers 34 to be used in the mercury relays may have orifices 4@ of the same size, but threaded to receive an insert such as a screw plug, the screw plug having an orifice already machined thereinto. Because of the self-lubricating properties of the material used for the studs 42 and for the container 12, the frictional resistance resulting due to the sliding action of plunger 34 is held to a minimum, thereby insuring the maintaining of consistent operating characteristics of the mercury relay according to the invention. In addition, no insulation between the various structural parts of the invention is necessary because of the materials used and location of the parts therein. For example, there is no possibility that armature portion 36 of the plunger 34 will come in Contact with the electrodes 14 and 16 because of the ceramic liner portion 38. Since the container 12 is made of electrically inert material, the compression spring 32 may be of metallic material and electrically conductive because even though in contact with the mercury pool 28 in the container 12, the spring 32 is completely isolated from any other electrically conducting element.

It will be further appreciated that due to the reduced frictional resistance between the plunger 34 and container 12, the strength of the eld necessary to cause the plunger 34 to rise in the container is decreased, thereby reducing the current necessary to be supplied to the coil 22. The reduction of the current load through coil 22 has the beneiicial effect of minimizing or lowering the heat produced therefrom and also permits a coil of reduced size to be used.

It is understood that the form of the invention herewith shown and described is merely an illustrative example of the same, it being understood that various modifications and changes in the arrangement of the parts may be resorted to without departing from the spirit of my invention, the scope of which is limited only by the appended claims.

What is claimed is:

l. A periodic mercury relay of the displacer type, comprising a pool of mercury, an envelope fabricated of material having the properties of being self lubricated and of an electrical insulator for said pool of mercury, said` envelope containing said pool of mercury, a pair of spaced electrodes mounted in said container, a mercury displacing element buoyant in said mercury pool and including a tubular armature portion and a liner portion of ceramic located inside said tubular portion, said liner portion being in the form of an inverted dome having a cap and having a metering orifice in the cap, means mounted on said mercury displacing element for establishing selflubricative sliding contact with said container, resilient means biasing said mercury displacing element below its position of natural buoyancy in said mercury pool, electromagnetic energizing coil means located in surrounding relationship to a portion of said container and which when energized, actuate said mercury displacing member against the bias of said resilient means so that the level of said pool of mercury drops below the level required to bridge said spaced electrodes in said container, and means connecting said spaced electrodes in series with said energizing coil.

2. A periodic mercury relay of the displacer type, comprising a pool of mercury, an envelope containing said pool of mercury, a pair of spaced electrodes mounted in said envelope, an inverted dome mercury displacing element in said envelope in self-lubricative sliding relationship therewith, said dome having a cap, said displacing element having an armature portion and a metering orifice in said cap, resilient means mounted in said container and biasing said displacing member below its normal position of buoyancy in said pool, and an energizing coil responsive to electrical conduction between said electrodes to actuate said displacing element against the bias of said resilient means, said electrical contact through the mercury between said electrodes being broken after displacement of a predetermined quantity of mercury -by said mercury displacing element through said metering orifice to thereby (le-energize said coil, said envelope being fabricated of self-lubricative material having electric insulating properties, and studs of self-lubricating material being secured to said plunger and bearing against said envelope.

3. A periodic mercury relay of the displacer type to periodically energize a load connected across the energizing coil thereof comprising a pool of mercury, an envelope containing said pool of mercury, a pair of spaced electrodes mounted in said enevelope Iand connected in series with the energizing coil, resilient means mounted in said envelope, a buoyant mercury displacing plunger biased by said resilient means downward into said pool of mercury and movable in response to the energization of said coil upward `against the bias of said resilient means, said plunger having metering orifice communicating with said pool of mercury, said electrodes being bridged by said mercury only on predetermined depression of said plunger into said pool of mercury, said orifice positioned to communicate with said pool of mercury in all positions of said plunger, said envelope being fabricated of self-lubricative material having electric insulating properties, and

studs of self-lubricating material being secured to said plunger and bearing against said envelope.

4. rhe relay of claim 3 wherein said envelope is fabricated of thermal insulating material.

5. Apparatus according to claim 4 wherein said envelope is fabricated of nylon filled with fiberglass.

6. Apparatus `according to claim 5 wherein said studs are fabrica-ted of nylon.

7. Apparatus according to claim 6 wherein said mercury displacing element includes a tubular outer armature portion and an inner liner portion of material having electrically insulating properties and in the form of an inverted dome having said orifice therein.

8. A mercury switch including an envelope, said envelope being fabricated of self-lubricative plastic material, said plastic material including a quantity of fiberglass, a poot of mercury in said envelope, said pool of mercury having its Iboundaries defined by the walls of said envelope, a displacement plunger slidably supported in said envelope, a magnetic sleeve mounted on said plunger, electrodes extending through the walls of said envelope, and selflubricative protrusions secured `to said sleeve and bearing against the inner wall of said envelope.

9. A mercury relay for opening and closing a circuit to a load, comprising an envelope containing la mercury pool, said envelope being fabricated of self-lubricative nylon filled with fiberglass, a hollow plunger open at its top `and closed at its bottom and buoyant in said pool, said plunger having plural nylon studs carried on its exterior surface, said studs being in contact with the interior wall of said envelope, depressive means normally maintaining said lhollow plunger depressed in said pool, said hollow plunger having a wall opening always communicating with said pool in all positions of said plunger, magnetic means secured to said hollow plunger, an eiectromagnet positioned when energized to raise said magetic member and hollow plunger against the face of said depressive means, said wall opening being a metering orifice for metered flow of mercury into said hollow plunger when said hollow plunger is depressed and out of said hollow plunger when said hollow plunger is raised, a first electrode `aligned with said open top and extending into said pool when said plunger is depressed and out of said pool after said plunger is raised, and at least one further electrode through a wall of said envelope.

10. The combination yaccording to claim 9 wherein said hollow plunger is positioned to maintain at least said first electrode immersed in said mercury during substantial flow of said mercury through said metering orifice.

11. The combination according to claim 9 wherein said electrodes are connected in series with said electromagnet.

References Cited in the tile of this patent UNITED STATES PATENTS 1,957,691 Callahan May 8, 1934 1,971,934 Hatay Aug. 28, 1934 2,450,780 Bucklen Oct. 5, 1948 2,658,124 Wehner Nov. 3, 1953 2,973,417 McKinney Feb. 28, 1961 

1. A PERIODIC MERCURY RELAY OF THE DISPLACER TYPE, COMPRISING A POOL OF MERCURY, AN ENVELOPE FABRICATED OF MATERIAL HAVING THE PROPERTIES OF BEING SELF LUBRICATED AND OF AN ELECTRICAL INSULATOR FOR SAID POOL OF MERCURY, SAID ENVELOPE CONTAINING SAID POOL OF MERCURY, A PAIR OF SPACED ELECTRODES MOUNTED IN SAID CONTAINER, A MERCURY DISPLACING ELEMENT BUOYANT IN SAID MERCURY POOL AND INCLUDING A TUBULAR ARMATURE PORTION AND A LINEAR PORTION OF CERAMIC LOCATED INSIDE SAID TUBULAR PORTION, SAID LINER PORTION BEING IN THE FORM OF AN INVERTED DOME HAVING A CAP AND HAVING A METERING ORIFICE IN THE CAP, MEANS MOUNTED ON SAID MERCURY DISPLACING ELEMENT FOR ESTABLISHING SELFLUBRICATIVE SLIDING CONTACT WITH SAID CONTAINER, RESILIENT MEANS BIASING SAID MERCURY DISPLACING ELEMENT BELOW ITS POSITION OF NATURAL BUOYANCY IN SAID MERCURY POOL, ELECTROMAGNETIC ENERGIZING COIL MEANS LOCATED IN SURROUNDING RELATIONSHIP TO A PORTION OF SAID CONTAINER AND WHICH WHEN ENERGIZED, ACTUATE SAID MERCURY DISPLACING MEMBER AGAINST THE BIAS OF SAID RESILIENT MEANS SO THAT THE LEVEL OF SAID POOL OF MERCURY DROPS BELOW THE LEVEL REQUIRED TO BRIDGE SAID SPACED ELECTRODES IN SAID CONTAINER, AND MEANS CONNECTING SAID SPACED ELECTRODES IN SERIES WITH SAID ENERGIZING COIL. 